Conventional golf balls have been designed to provide particular playing characteristics. These characteristics are generally initial velocity, compression, and spin of the golf ball, and they can be optimized for various types of players. For instance, certain players prefer a ball that has a high spin rate in order to control the ball flight and stop the golf ball on impact with the greens. This type of ball, however, may not provide maximum distance. Other players prefer a ball that has a low spin rate and high resiliency to maximize distance.
Generally, golf balls have been classified as wound balls or solid balls. Wound balls are generally constructed from a liquid or solid center surrounded by an elastic thread wound in tension to form a wound core. This wound core is then surrounded by a cover. Wound balls are generally thought of as performance golf balls. When struck by a golf club, these balls have good resiliency, relatively high spin rate, and “soft” feel. Wound balls are generally more difficult to manufacture than solid golf balls.
Some early solid or non-wound golf balls contained metal. U.S. Pat. No. 4,995,613 to Walker discloses a practice golf ball with a dense metal-containing core surrounded with a thick layer of resilient material. To this, a fabric cover is bound. U.S. Pat. No. 5,104,126 to Gentiluomo discloses a non-wound ball that includes a dense center of steel surrounded by a molded encapsulating mass of a low density resilient synthetic elastomer composition. Both of these patents disclose solid or non-wound balls that include metal.
On the other hand, U.S. Pat. No. 1,946,378 to Young and U.S. Pat. No. 2,914,328 to Harkins disclose golf balls that include wound layers. For example, the Young patent discloses a spherical center weight of metal with an intermediate sphere of soft rubber thereon. Windings of rubber are disposed about the intermediate layer and an outer casing is formed thereon. Since high cis, polybutadiene was first introduced in 1956, the Young patent that was filed in 1931 and issued in 1934, did not disclose the use of such a compound. The commercial product related to the Harkins patent was the First Flight™ golf ball. The Harkins patent does not disclose the use of polybutadiene and the First Flight™ balls were not manufactured using polybutadiene.
TABLE IPrior Art Steel Centered Golf BallsInner SphereOuter SphereCenterName of BallDiameterWeightHardnessDiameterWeightSide StampMaterial(in)(oz)Material(Shore D)(in)(oz.)First Flight Reg 90steel0 3430.096NR42.51 0340 549Steel Powered CenterFirst Flight Reg 100steel0 3430 097NR36.11 0570.541Steel Powered CenterFirst Flight 90+steel0 3420 096SBR & NR35.11.0660.514Steel Powered CenterMade in USARoyce Chemicalsteel0 3430 096SBR & NR51 11 0050 514Steel Flightsteel0 3140.074NR30 71 000.494Steel CenterByron Nelsonsteel0 3460 100NR24 71 2490 731Steel CenterPlymothsteel0.3430 097SBR & NR28 61.0550 556ChampionshipSteel CenterButchart-Nichollssteel0.3430.096SBR & NR37 11 0050 526Steel MasterSteel CenterKroydonsteel0 3180 076NR & SBR48.11 240 720Steel CenterUS. Fortunesteel0 3430 096SBR & NR34.21.0500.560Steel CenterLong Wearsteel0 3480 102NR30 31 2200 724Steel CenterBridgestone Msteel0 3450.097NR & SBR37 21.0720 542H V. Metallic
The balls in Table I are formed with a steel inner sphere surrounded by an outer sphere or shell to form a center. The outer sphere is formed of natural rubber, designated NR, and possibly styrene butadiene rubber, designated SBR. No polybutadiene is used.
In conventional balls, when polybutadiene forms a core layer of the golf ball it typically includes enough high density fillers to alter the weight of such a layer. The amount of high density fillers used is, however, less than about 10 parts per hundred based upon 100 parts per hundred of polybutadiene. These fillers have two unfortunate side effects, they increase the hardness of the center and reduce the ball's resiliency.
Therefore, a need exists for a golf ball with lower hardness or compression but with greater resiliency. The improved golf balls of the present invention to provide as disclosed herein provides such a golf ball.